I would like to remove all the header on category pages (icon and title) but don't know how to do it.

I tried this with CSS Custom :

.archive-header {
content: none;
}

but obviously that doesn't work ^^'
Maybe it's not only in the CSS

I also would like to remove the line where is wrote : posted by "user" the "date"
This line is displayed on post but i don't know where i can find it
I think this task is pretty easy but it look like i'm pretty bad ^^'